1. AP Bio Exam Review: Cell Energy (Respiration & Photosynthesis)

2. Catabolic pathways release energy by breaking down complex molecules into simpler compounds
C6H12O6 +6O H2O + 6CO2 +E
Anabolic pathways consume energy to build complex molecules from simpler ones
6H20+6CO2 + E C6H12O6 +6O2

3. A cell does three main kinds of work: Mechanical Transport Chemical
Concept 8.3 ATP powers cellular work by coupling exergonic reactions to endergonic reactions
A cell does three main kinds of work:
Mechanical
Transport
Chemical
To do work, cells manage energy resources by energy coupling, the use of an
exergonic (energy releasing) process to drive an endergonic (energy absorbing) one

4. Concept 8.4: Enzymes speed up metabolic reactions by lowering energy barriers
A catalyst is a chemical agent that speeds up a reaction without being consumed by the reaction
An enzyme is a catalytic protein
Hydrolysis of sucrose by the enzyme sucrase is an example of an enzyme-catalyzed reaction

5. Substrate Specificity of Enzymes
The reactant that an enzyme acts on is called the enzyme’s substrate
The enzyme binds to its substrate, forming an enzyme-substrate complex
The active site is the region on the enzyme where the substrate binds

8. Cofactors Enzyme Inhibitors
Cofactors are nonprotein enzyme helpers such as minerals
Coenzymes are organic cofactors such as vitamins
Enzyme Inhibitors

9. Allosteric Regulation
a protein’s function at one site is affected by binding of a regulatory molecule at another site
Allosteric regulation may either inhibit or stimulate an enzyme’s activity

10. Feedback Inhibition
In feedback inhibition, the end product of a metabolic pathway shuts down the pathway

11. Energy Harvest
Energy is released as electrons “fall” from organic molecules to O2
Broken down into steps:
Food  NADH  ETC  O2
Coenzyme NAD+ = electron acceptor
NAD+ picks up 2e- and 2H+  NADH (stores E)
NADH carries electrons to the electron transport chain (ETC)
ETC: transfers e- to O2 to make H2O ; releases energy

12. Cellular Respiration

13. Mitochondrion Structure
Citric Acid Cycle
(matrix)
ETC
(inner membrane)

14. Glycolysis Without O2 O2 present Fermentation Respiration
Occurs in plants and animals
Occurs in cytosol
Keep glycolysis going
No oxygen needed
Creates alcohol [+ CO2] or lactic acid
Release E from breakdown of food with O2
Occurs in mitochondria
O2 required (final electron acceptor)
Produces CO2, H2O and up to 38 ATP (NADH, FADH2)

15. PURPOSE = NAD+ recycled for glycolysis
Types of Fermentation
Alcohol fermentation
Lactic acid fermentation
Pyruvate  Ethanol + CO2
Ex. bacteria, yeast
Used in brewing, winemaking, baking
Pyruvate  Lactate
Ex. fungi, bacteria, human muscle cells
Used to make cheese, yogurt, acetone, methanol
Note: Lactate build-up does NOT causes muscle fatigue and pain (old idea)
PURPOSE = NAD+ recycled for glycolysis

16. Various sources of fuel
Carbohydrates, fats and proteins can ALL be used as fuel for cellular respiration
Monomers enter glycolysis or citric acid cycle at different points

17. ENERGY glycolysis Respiration Krebs cycle fermentation ethanol + CO2
aerobic (with O2)
anaerobic (without O2)
glycolysis
(cytosol)
Respiration
(mitochondria)
substrate-level phosphorylation
Krebs cycle
(citric acid cycle)
fermentation
electron transport chain
Oxidative Phosphorylation
ethanol + CO2
(yeast, some bacteria)
lactic acid
(animals)
chemiosmosis

18. Sites of Photosynthesis
Leaf cross section
Vein
Mesophyll
Stomata
CO2 O2
Mesophyll cell
Chloroplast
5 µm
Outer
membrane
Intermembrane
space
Inner membrane
Thylakoid
Granum
Stroma
1 µm
mesophyll: chloroplasts mainly found in these cells of leaf
stomata: pores in leaf (CO2 enter/O2 exits)
chlorophyll: green pigment in thylakoid membranes of chloroplasts

19. Photosynthesis = Light Reactions + Calvin Cycle

20. Light Reactions

22. Both respiration and photosynthesis use chemiosmosis to generate ATP

23. Calvin Cycle = produce 3C sugar (G3P)

24. Photorespiration: low carbon-fixation when stomata closed in hot, dry climate
CAM
C fixation & Calvin together
C fixation & Calvin in different cells
C fixation & Calvin at different TIMES
Rubisco
(normally fixes CO2)
PEP carboxylase fixes CO2
Organic acid
Mesophyll cells
Mesophyll: fix CO2
Bundle Sheath: Calvin Cycle
Night: fix CO2 in 4C acids
Day: Calvin Cycle
Ex. rice, wheat, soybeans
Ex. sugarcane, grass
Ex. cacti, pineapple, succulent

25. Comparison RESPIRATION PHOTOSYNTHESIS Plants + Animals
Needs O2 and food
Produces CO2, H2O and ATP, NADH
Occurs in mitochondria membrane & matrix
Oxidative phosphorylation
Proton gradient across membrane
Plants
Needs CO2, H2O, sunlight
Produces glucose, O2 and ATP, NADPH
Occurs in chloroplast thylakoid membrane & stroma
Photorespiration
Proton gradient across membrane